I think you can do it without drainage, but drainage makes things so much easier.
It does not have to be hard unless your enclosure has a glass bottom. Just purchase a cheap table (Ikea has them) that your cage will sit on. Cut a good size hole in the table. Put a bucket or deep rubber pan under the hole. Put the cage on the table, drill 3 or 4 holes over the hole in the table. Put something heavy near the holes in the bottom of the cage. Voila, you have a drainage system.